Background A low level of cardiorespiratory fitness [CRF; typically defined as peak oxygen uptake (VO2peak) or peak power output (PPO)] is a widely reported consequence of spinal cord injury (SCI). This systematic review with meta-analysis and meta-regression aimed to assess whether certain SCI characteristics and specific exercise considerations are moderators of changes in CRF. Methods Eligible studies included randomised controlled trials (RCTs) and pre-post studies that conducted an exercise intervention lasting >2 weeks. The outcome measures of interest were absolute (AVO2peak) or relative VO2peak (RVO2peak), and/or PPO. Four databases were searched up to July 2021. The Cochrane Risk of Bias 2 tool and the National Institute of Health Quality Assessment Tool were used to assess bias/quality. The certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Random effects meta-analyses and meta-regressions were conducted. Results Ninety studies (110 independent exercise interventions) with a total of 1,191 participants were included in our primary meta-analysis. There were significant improvements in AVO2peak [0.22 (0.17, 0.26) L/min, p<0.001)], RVO2peak [2.8 (2.2, 3.4) mL/kg/min, p<0.001)], and PPO [11 (8, 13) W, p<0.001]. There were no subgroup differences in AVO2peak or RVO2peak. There were subgroup differences (p<0.008) for changes in PPO based on time since injury, neurological level of injury, exercise modality, relative exercise intensity, method of exercise intensity prescription, and frequency. The meta-regression found that increased age was associated with increases in AVO2peak and RVO2peak, and exercise intensity prescription and volume were associated with increases in PPO (p<0.05). GRADE assessments indicated a low level of certainty in the estimated effects due to study design, risk of bias, inconsistency, and imprecision. Conclusion The pooled analysis indicates that performing exercise >2 weeks results in significant improvements in AVO2peak, RVO2peak and PPO in individuals with SCI. Subgroup comparisons identify that upper-body aerobic exercise and resistance training appear the most effective at improving PPO. Furthermore, acutely-injured, individuals with paraplegia, exercising at a moderate-to-vigorous intensity, prescribed via a percentage of oxygen consumption or heart rate, for more than 3 sessions/week will likely experience the greatest change in PPO. Registration PROSPERO CRD42018104342

The authors have declared no competing interest.

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=104342)

Daniel Hodgkiss is supported by a Nathalie Rose Barr PhD studentship (#NRB123) from the International Spinal Research Trust (ISRT), a registered charity in the UK. Gurjeet Bhangu was supported by the Faculty of Medicine within the University of British Columbia (UBC) via the Flexible and Enhanced Learning Program. Carole Lunny’s postdoctoral work is supported by a CIHR project grant (2021-2023). Catherine Jutzeler was supported by the Swiss National Science Foundation (Ambizione Grant [PZ00P3_186101]) and Wings for Life (Wings for Life Research Foundation [#ID 2020_118]). Tom Nightingale (grant number 17767) and Matthias Walter (grant number 17110) were recipients of Michael Smith Foundation for Health Research Trainee Awards in conjunction with the International Collaboration on Repair Discoveries and Rick Hansen Foundation, respectively.

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